I agree. Your problem seems to be within yourself. You are in grave danger of creating the very things you most fear. Your jealousy is isolating your family from normal friendships and relationships. At some point, your husband will have had enough! As your kids get older, and going through the normal separations of the teen years, they too will withdraw from you.
What you are calling “jealousy” is actually very deep-seated insecurity. Either something happened to you that makes you feel that the people you love will abandon you or you have a personality disorder that makes you emotionally unstable – or both. I can’t make a diagnosis on the basis of what you’ve written. But a mental health counselor can.
I hope your family means enough to you for you to go get an evaluation. There is still time to fix this. So far, your husband is somehow tolerating your fears and is generally supportive. Your children are still young. With some work, you can save your marriage and keep your family together. But it won’t happen without the work. I suggest you take your letter and this response to the first session. It will give your therapy a jump-start.
I applaud you for writing. You probably had to work up your courage to admit that you have a problem. Hold onto that strength and call to make an appointment with a therapist today.
I wish you well.